Apparatus for the low-loss wiring of the semiconductor switching elements of a three-level inverter

Claim 1

An apparatus for relieving semiconductor switching elements of one stage of a neutral-point-clamped PWM inverter of large voltage changes during a switching-off process, said inverter stage including a series arrangement of first, second, third and fourth antiparallel circuits each containing a semiconductor switching element and a bypass diode, a junction point between the second and the third antiparallel circuits serving as a stage output, the inverter stage receiving input from a d-c voltage source having positive and negative potentials via a first and second switching-on relief choke coil coupling the ends of the series arrangement to said d-c voltage source, two voltage divider capacitors coupled in series across the d-c voltage source, and first and second coupling diodes coupling the junction point of said voltage divider capacitors to junction points between the first and second, and third and fourth antiparallel circuits, the relieving apparatus comprising: (a) third and fourth switching-on relief choke coils for limiting the current rate of rise, coupled in series respectively with the first and second coupling diodes coupling said first and second coupling diodes to said junction point of the two voltage divider capacitors, (b) a switching-off relief capacitor having one terminal connected to the stage output, (c) first and second wiring capacitors with one terminal of said first wiring capacitor being coupled to the end of the series arrangement which is coupled to the positive potential, and one terminal of said second wiring capacitor being coupled to the end of the series arrangement that is coupled to the negative potential of the d-c voltage source, (d) first and second d-c consumers which couple the other terminals of said first and second wiring capacitors to the junction point of the two voltage divider capacitors, and (e) a diode network having: first and second wiring diodes which couple a fictitious center at the other terminal of the switching-off relief capacitor respectively to a junction point between the first coupling diode and the third switching-off relief choke coil, and a junction point between the second coupling diode and the fourth switching-on relief choke coil; third and fourth wiring diodes coupling the fictitious center respectively to a junction point between the first wiring capacitor and the first d-c consumer, and to a junction point between the second wiring capacitor and the second d-c consumer; and fifth and sixth wiring diodes which respectively couple the junction point between the first wiring capacitor and the first d-c consumer to the junction point between the first and second antiparallel circuit; and the junction point between the second wiring capacitor and the second d-c consumer to the junction point between the third and fourth antiparallel circuit.

Claim 2

An apparatus for relieving semiconductor switching elements of one stage of a neutral-point-clamped PWM inverter of large voltage changes during a switching-off process, said inverter stage including a series arrangement of first, second, third and fourth antiparallel circuits each containing a semiconductor switching element and a bypass diode, a junction point between the second and the third antiparallel circuits serving as a stage output, the inverter stage receiving input from a d-c voltage source having positive and negative potentials via a first and second switching-on relief choke coil coupling the ends of the series arrangement to said d-c voltage source, two voltage divider capacitors coupled in series across the d-c voltage source, and first and second coupling diodes coupling the junction point of said voltage divider capacitors to junction points between the first and second, and third and fourth antiparallel circuits, the relieving apparatus comprising: (a) third and fourth switching-on relief choke coils for limiting the current rate of rise, coupled in series respectively with the first and second coupling diodes coupling said first and second coupling diodes to said junction point of the two voltage divider capacitors, (b) a switching-off relief capacitor having one terminal connected to the stage output, (c) first and second wiring capacitors with one terminal of said first wiring capacitor being coupled to the end of the series arrangement which is coupled to the positive potential, and one terminal of said second wiring capacitor being coupled to the end of the series arrangement that is coupled to the negative potential of the d-c voltage source, (d) first and second d-c consumers which couple the other terminals of said first and second wiring capacitors to the junction point of the two voltage divider capacitors, and (e) a diode network having: first and second wiring diodes which couple a fictitious center at the other terminal of the switching-off relief capacitor respectively to a junction point between the first coupling diode and the third switching-off relief choke coil, and a junction point between the second coupling diode and the fourth switching-on relief choke coil; third and fourth wiring diodes coupling the fictitious center respectively to a junction point between the first wiring capacitor and the first d-c consumer, and to a junction point between the second wiring capacitor and the second d-c consumer; and fifth and sixth wiring diodes which respectively couple the junction point between the first wiring capacitor and the first d-c consumer to the junction point between the first and second antiparallel circuit; and the junction point between the second wiring capacitor and the second d-c consumer to the junction point between the third and fourth antiparallel circuit.